Started bisect job https://chromeperf.appspot.com/buildbucket_job_status/9002886081387975232

Running another bisect to get the exact regression numbers.

=== Auto-CCing suspected CL author lpy@chromium.org ===

Hi lpy@chromium.org, the bisect results pointed to your CL below as possibly
causing a regression. Please have a look at this info and see whether
your CL be related.


===== BISECT JOB RESULTS =====
Status: completed


===== SUSPECTED CL(s) =====
Subject : [Reland][Tracing] Embed V8 runtime call stats into tracing.
Author  : lpy
Commit description:
  
Currently we have V8 RuntimeCallStats that is independently from tracing when
running d8 with flag --runtime_call_stats. This patch embeds V8 runtime call
stats into tracing, by having a global table of runtime call counters each
isolate, resetting the table each time we enter a top level trace event, and
dumping the table for each top level trace event. This will make trace file more
compat, as well as enable runtime call stats in tracing system.

This patch adds ~5% overhead to V8 when the category is enabled, we measure the
overhead by running a script when category is enabled.

BUG= v8:5089 

Committed: https://crrev.com/d014866173eaa2b548c566217b2c94b1d49385fa
Committed: https://crrev.com/1ca3b73bba4a7253ca8eeef39321d70e7d414331
Committed: https://crrev.com/3f936a5b17754783e92d2146eaf66c88a78ee45b
Review-Url: https://codereview.chromium.org/2187693002
Cr-Original-Original-Original-Commit-Position: refs/heads/master@{#38270}
Cr-Original-Original-Commit-Position: refs/heads/master@{#38314}
Cr-Original-Commit-Position: refs/heads/master@{#38403}
Cr-Commit-Position: refs/heads/master@{#38510}
Commit  : 7a3631e7e12fe0e5038d80c58f3f491c61977b95
Date    : Wed Aug 10 01:19:01 2016


===== TESTED REVISIONS =====
Revision                       Mean     Std Dev   N  Good?
chromium@411049                32.217   2.62381   5  good
chromium@411060                31.2104  0.750249  5  good
chromium@411066                32.0252  0.902565  5  good
chromium@411066,v8@5caabdd5cc  31.8812  1.08795   5  good
chromium@411066,v8@7a3631e7e1  54.696   1.68527   5  bad    <--
chromium@411066,v8@400f03ab97  54.6702  1.1699    5  bad
chromium@411066,v8@93809055aa  55.238   1.18043   5  bad
chromium@411066,v8@ca9ec36eb5  55.4856  2.44095   5  bad
chromium@411066,v8@9e14155da9  53.7062  1.01428   5  bad
chromium@411067                54.3564  2.41463   5  bad
chromium@411068                53.7988  0.681363  5  bad
chromium@411069                53.2856  2.07813   5  bad
chromium@411071                55.5418  1.35874   5  bad
chromium@411093                53.2794  1.46643   5  bad

Bisect job ran on: linux_perf_bisect
Bug ID: 642373

Test Command: src/tools/perf/run_benchmark -v --browser=release --output-format=chartjson --upload-results --also-run-disabled-tests v8.todomvc
Test Metric: v8_execution_cpu_self_sum/Polymer
Relative Change: 65.38%
Score: 99.9

Buildbot stdio: http://build.chromium.org/p/tryserver.chromium.perf/builders/linux_perf_bisect/builds/6680
Job details: https://chromeperf.appspot.com/buildbucket_job_status/9002886081387975232


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Graphs recovered.

I believe this issue has been fixed once that CL landed https://codereview.chromium.org/2301743002 which put back the events that were removed.

It sounds counter intuitive, but it is not. The regression happened on a self time, that is calculated based on removing the time of the children. As we added back the trace-events that were removed, the children were added back.

lpy@ can you verify that everything is now in order and close this bug?

Also can you figure out why the ref build stopped producing time ~ the same time.

The ref build stopped producing result because it was disabled in https://codereview.chromium.org/2304113002/ because of https://bugs.chromium.org/p/chromium/issues/detail?id=636405

I already reverted it in https://codereview.chromium.org/2313143002/

Close this issue as fixed since the graph is back to normal.